Donald Trump will be the 45th U.S. president. His victory in the presidential election deeply shocked not just Americans, but the entire world. I once shrugged off Brexit as a temporary upset in the regional order, but Trump's victory means the world's leading country has begun to deviate from the existing world order. The whole international community, including the U.S., is now drifting into uncharted territory. The impact of an unpredictable Trump presidency will be substantial and, perhaps, even devastating. South Korea is no exception. It is deeply concerned about how to deal with the next U.S. leader, well known for his eccentricity and unpredictability, and how his presidency will affect the future of its alliance with the U.S. as well as its relations with China.

Trump's surprise victory is not good news for the U.S.-led global order. It actually represents America's tarnished prestige and shrinking influence on the international stage. One can even say the latest U.S. election signals the superpower's fall from grace. Just as the President-elect noted, the U.S. no longer has the same power as it did a few decades ago. It is now preoccupied with resolving its pressing domestic issues. Trump's "America First" policy may sound catchy, but it actually represents isolationism and trade protectionism. President Trump will refrain from over-the-top remarks and absurd behavior, but his policies will remain the same.

It is noteworthy that individuals' characteristics are relevant to the way they think and behave. We in South Korea are no stranger to how our former and current presidents have been influenced by their own backgrounds and characteristics in their leadership styles. For instance, Seoul's incumbent leader Park Geun-hye grew up in de-facto isolation inside Cheong Wa Dae and thus has very few personal ties. This is a sign of her fragility as a leader. Her characteristics are some of the factors that contributed to one of the nation's biggest-ever cronyism scandals involving Park's confidant Choi Soon-sil, who faces accusations of meddling in state affairs without any official title and peddling influence for personal gain. In comparison, the new U.S. leader was a real estate tycoon and therefore has a practical mindset. Also doubling as an entertainer on TV shows, he can even be dramatic. Under his presidency, America will act very selfishly. Also, if unfavorable situations arise at home and abroad, the President-elect will try to distract public attention by creating some other events.

The rest of the world is busy figuring out the impact of a Trump presidency. China, the key Asian rival for the US, has more to gain than lose from his leadership. First, his victory has shattered the illusion of the US political system. The world was witnessing as the U.S. received this unproven political firebrand with much enthusiasm. This even makes the Chinese political system look more plausible, where nurturing top leaders can take decades. Second, Beijing, so far overshadowed by U.S. President Barack Obama's so-called "smart" diplomacy, is now ready to outshine Washington in the diplomatic rivalry. Trump likes to put pressure on others rather than respect them, often triggering their animosity. His foreign policy will most likely be an upgraded version of former U.S. President George W. Bush's hard-line stance dubbed "cowboy diplomacy." Whether intended or not, Trump's unpredictable character will cover up China's diplomatic mistakes and weaknesses under President Xi Jinping's leadership. Third, Trump helps China lay the groundwork for a new world order. Xi would even appear to be a more serious leader than Trump. The Chinese President has presented various initiatives like the new Asian security concept, the Belt and Road initiative, and the AIIB, while Trump seems more like a businessman than a nation's commander-in-chief.

South Korea enjoyed its best-ever relations with China until last year when their ties soured quickly when Seoul announced the deployment of the US Terminal High-Altitude Area Defense (THAAD) system on its soil in the wake of North Korea's nuclear and missile tests early this year. As a matter of fact, Trump's threat to pull U.S. Forces out of the South is actually his way of demanding more payment from Seoul to cover the cost of its military presence. What is more, Trump's indication of possible talks with the North's leader Kim Jong-un is a prelude to more surprises in store for the future U.S. policy towards the Korean Peninsula. In this vein, the South's decision to deploy THAAD might also be subject to reconsideration. Yet, if Seoul retracts its announcement on its own, the US will begin to question the country's value as a long-standing ally, and China may assume the South lacks its own principles and is therefore easy to control. If the changing political landscape in the U.S., rather than Seoul's change of mind, puts the decision under scrutiny, Seoul and Beijing will be able to defuse bilateral tensions.

In the longer term, fundamental changes might be ahead for the ROK-U.S. alliance. For Washington, Seoul is not as important an ally as Tokyo. The South was not as active as other Asian countries in embracing and assisting the U.S. strategic rebalance to the region, and it was even reluctant to clarify its position on the disputes in the South China Sea. Trump will not undermine the alliance as long as Seoul pays its fair share for the U.S. military presence here and shows a willingness to revise the current bilateral trade deal in place. Yet the existing idea that the U.S. is the linchpin for South Korea's security will lose momentum. Currently, the South relies for its security on the U.S. and its economic prosperity on China, but what if questions arise over Washington's commitment to its ally's defense? Materialism, a concept so far unfamiliar to South Korea in its alliance with the U.S., will affect the value of their bilateral relations. If the U.S. is no longer the reliable ally like in the old days, the seemingly solid alliance will gradually fall apart.

Changes in the U.S. political scene are bringing a major upheaval in the South's security environment. Trump's weakness lies in foreign policy, and he therefore needs to nominate foreign policy advisors first and foremost. Once a new foreign policy team is formed, its primary focus would be on dealing with the great powers such as China, Japan, and Russia. In comparison, middle-power nations like South Korea will take a back seat. Trump can send a friendly gesture to Kim Jong-un whenever he feels like it. Seoul must rethink its policies on foreign relations, Pyeongyang, and Korean unification, and in doing so, it must take the new U.S. leader into account. The question remains: Are we ready to do this? I am deeply concerned about whether the South Korean government, now stuck in a deadlock over the Choi scandal, will be able to take any pre-emptive diplomatic measures.

Hwang Jae-ho is professor of international studies, Hankuk University of Foreign Studies.